Meanwhile, property developer Mori Building Co. has found buyers for almost all its seventy prime Toranomon Hills apartments that came to market in June, a year-and-a-half before schedule, according to Kosei Ajima, the developer's general manager of the residential business promotion unit.

Buyers galore

There is no shortage of buyers. Mitsubishi Real Estate's Sakai, who is now in charge of selling the Parkhouse Nishishinjuku Tower60 complex, located near the Tokyo Metropolitan Government Building in Shinjuku with prices starting at 31 million yen for one room studio flats, said "we've already received several offers" for the most expensive penthouses that will be sold for around 350 million yen.

The strong demand by luxury home buyers is a bright spot in the property sector, which has taken a beating following the nationwide consumption tax rate hike to 8 percent from 5 percent in April.

"We believe the stock market rally since Shinzo Abe came to power in December 2012 has increased the wealth of the richest Japanese," says Hiroyuki Miyamoto, senior consultant at Nomura Research Institute (NRI). The Nikkei, the benchmark stock index, has surged 72 percent since the end of November 2012.

Nearly one million households in Japan owned financial assets of between one and five hundred million yen ($837,830 – $4.2 million) in 2013, up 25.4 percent on 2011, according to NRI's figures. Combined with the 8 percent rise in the number of "super-rich" households, the value of assets held by the wealthy has surged 28.2 percent to 241 trillion yen.

And they are putting a chunk of that money into the small number of newly built luxury apartments coming to market in prime Tokyo residential areas, according to Miyamoto.

Abenomics not the only reason

Analysts say a supply shortage is also fueling the strong sales. "The availability of plots large enough to build new apartment complexes in central Tokyo is very limited," said Daisuke Kitai, spokesperson at Nomura Real Estate Development.

Nomura Real Estate's next luxury project, for example, with apartments at up to 500 million yen, will only come to market in the middle of 2015, while Mori Building's next residential project is currently under construction, with sales slated to begin in September.